An automotive transmission alters the power generated by a vehicle's engine and transmits the resultant power to a drive shaft, which turns the vehicle's wheels. Transitioning between one or more gears within some transmissions is made possible by the use of a transmission servo assembly. Generally, the transmission servo assembly applies a servo pin to a braking mechanism, which locks a portion of the gear train, thereby assisting a gear change. For example, in FIG. 1 there is shown a prior art transmission 10 including a servo assembly 20 and a band 12 that is applied by the servo assembly to shift the vehicle between low and high gears. Band 12 wraps about a reverse input drum 14 (only partially shown), which has one end anchored to a case 16 of transmission 10 by a band anchor pin 18. Input drum 14 is coupled to a reaction sun shell which is splined to a reaction sun gear (not shown). When band 12 is applied by the servo assembly 20 (moving the pin portion of the servo assembly out of the page as seen in FIG. 1), input drum 14, the reaction sun shell, and the reaction sun gear are all held stationary, thus facilitating the engagement of one of the gears.
To improve the transition between gears, automotive enthusiasts may seek to increase the fluid pressure within such a servo assembly. For example, for high performance transmissions, fluid pressures of 300 psi or more are typical operating pressures. Increasing the fluid pressure, however, requires that additional energy to drive the fluid pump to obtain the desired fluid pressure—energy that would otherwise be used to propel the car forward. In some automotive servo assemblies operating under high pressures, the configuration of the assembly does not provide for effective or complete removal of the apply pressure from the piston, and consequentially the servo pin. This incomplete retraction of the servo pin is further exacerbated by the increased operating fluid pressure, which further unbalances the pressure differences within the servo assembly, thereby increasing the risk of band drag, e.g., band 12 does not fully release from input drum 14, considerably. Band drag leads to band failure and thus an inability to shift gears.